Retinoids play an essential role in controlling the normal growth and differentiation of various tissues and are therefore important for prevention and treatment of premalignant and malignant lesions. It has even been found that retinoids can cause cellular repair of hyperplastic, metaplastic and dsyplastic lesions caused by carcinogens. Moreover, retinoid deficiency has been shown to enhance susceptibility to chemical carcinogenesis. Indeed, retinoids are essential for the normal cellular growth and differentiation of epithelial tissues where more than half of the total primary cancers develop in both men and women. These epithelial tissues include the mouth, bronchi, larynx, pharynx, breast, esophagus, stomach, colon, uterus, kidney, bladder, testis, prostate, pancreatic ducts and skin. In the absence of retinoids in the diet, normal cellular growth and differentiation is disturbed.
The developments in this field, which are summarized above, are discussed in an article entitled "Prevention of chemical Carcinogenesis by Vitamin A and its Synthetic Analogs (Retinoids)", Federation Proceedings, 35, (May 1, 1976), 1332-1338.
While retinoid-type compounds have been found to be effective in treating carcinomas, and inhibiting the progression of premalignant or precancerous lesions to carcinomas, many of these retinoids have high toxicity and produce deleterious adverse effects such as hypervitaminosis A. The toxicity and adverse effect profile of many of these retinoids make them unsuitable for use in the treatment and prevention of cancer at high dosage levels where their effects are greatest. Therefore, it is desired to provide a retinoid type compound which will exhibit the tumor inhibiting effect of retinoids without the toxic manifestation or adverse effects generally associated with such retinoids.